Found these among my books in the storage unit. I used to read these in fascination when I was 8-14 years old. Probably bought at Tandy in Birmingham or Bedford in England by my Dad and I "nicked" them (probably with strong encouragement) after he read them!
I think I'm going to scan these. They seem quite fragile.
@kelpana
A generation of hobbyists scrawl schematics on graph paper as a result...
@vk3kri Yes, I had several maths copy books dedicated to those sorts of drawings!